Research On The Influencing Factors Of Kiwifruit Wine Color During Fermentation And Color Protection

The kiwifruit juice can be used to produce kiwifruit wine throughfermentation.However,the wine produced in this way was prone to browningduring its process.In this paper,the browning reason of kiwifruit wine and its color protection were studied,the conclusions are as follows:1.By measuring the change of chlorophyll,activity of enzyme and and the change of content in terms of phenols and acids during kiwi wine fermentationprocess,with statistical analysis of the correlation degree of the color parameters.The main factors affecting the color change were the degradation of chlorophyll and enzymatic browning during kiwifruit wine fermentation.2.The changes of chlorophyll and its derivatives were measured by HPLC.The chlorophyll and its derivatives were detected during the fermentation process.According to the results of detection of chlorophyll and its derivatives duringfermentation,the main degradation product of chlorophyll was pheophytin during fermentation.3.The enzymatic properties of kiwifruit polyphenol oxidase were studied.The results showed that the optimal pH and temperature for this enzyme was 6.5 and27?.High temperature treatment could inhibit PPO activity.Enzymatic reaction accorded with the Michaelis-Menten equation,with Km and Vmax values of 0.027mol/L and 38.61U/min,respectively.Cu²⁺,Mg²⁺,and Fe²⁺had the activation ofkiwifruit PPO,Zn²⁺inhibited the kiwifruit PPO,and Ca²⁺had no significant effect of kiwifruit PPO.L-cysteine exhibited stronger inhibition effect on PPO activity than phytic acid,EDTA-Na₂,and Vc.4.The fermentation technology of kiwifruit wine was optimized.Four factors influencing alcoholic fermentation and color difference of kiwifruit wine werestudied:SO₂ dosage,pH,temperature and fermentation time.Based on single-factor test,Orthogonal optimization experiment was designed.The optimumFermentation Conditions was:pH 3.8,SO₂ dosage 80mg/L,fermentationtemperature 14?and ferment 14 day.Compared with ordinary temperature,the content of polyphenols and Vc are higher in low temperature fermentation kiwi wine.The variety and content of flavor substances are more abundant and the quality is better.5.In order to inhibit the Browning of kiwi fruit wine,Sodium isoascorbate?L-cysteine?citric acid?EDTA-Na₂?GSH and Kojic acid were selected.Based on the results,the order of influence on the inhibition rate of kiwifruit wine Browning was L-cysteine>Sodium isoascorbate>citric aci d>EDTA-Na₂>GSH>Kojicacid.The order of influence on the color difference of kiwifruit wine was Sodium isoascorbate>L-cysteine>citric acid>EDTA-Na₂>GSH>Kojic acid.The three inhibitors with the greatest effects on browning inhibition and chroma wereSodium isoascorbate,L-cysteine,and phytic acid.The experimental data were analyzed by response surface regression using Design-Expert V8.0.6.1.Theresults showed that the best browning inhibitor for kiwifruit wine was obtained by the combined use of 0.612g/L Sodium isoascorbate,0.873/L L-cysteine,0.021%citric acid.The predicted value of browning inhibition rate using the optimizedcombination of browning inhibitors was 62.04%,the chroma value was 21.22.